This invention relates to a radial face seal for effecting a seal between relatively rotatable members such as a shaft and a housing which will control the leakage of the fluid from one region of high pressure to a second region of lower pressure. Radial face seals are well known in the art and are essentially formed with two face elements. One of the elements is fixed so that no movement occurs axially relative to the shaft, and this is referred to as a fixed seat. The other element is movable axially along the shaft and is sometimes referred to as a floating element or, in this particular case, to a nose piece. The elements are located in opposed relationship to each other and are arranged so that, in response to fluid pressure, spring pressure, or both, a sealing relationship will be obtained between them to prevent leakage out along the shaft. It has been shown that a mechanical seal is best obtained when the elements are not in direct physical contact with each other but rather when a thin lubricating fluid film is provided between their opposed face surfaces. This fluid film prevents or reduces wear due to direct mechanical contact and avoids the possiblity of mechanical damage or failure. However, the thickness of the fluid film must not be too large to cause excessive leakage and thus, the thickness of the film is controlled by the precise geometry of the face surfaces. In one of the popular arrangements, a lift pad is provided which consists of shallow recesses in the face of the seal and the dimensions of these recesses are critical and difficult to manufacture because of the tight tolerances that are required. Also, any contaminant in the fluid has a significant detrimental effect on the performance of the seal. Accordingly, the hydrodynamic performance range is limited because of the fixed geometry in this structure.
There remains a need therefore in the art to have a controllable mechanical seal where the thickness of the lubricating fluid film can be maintained at a practical thickness and one in which the manufacturing tolerances are reduced. It is further desirable to have a seal arrangement where contaminants are less likely to impact upon the performance of the seal, and, one in which the seal can self adjust for any shaft misalignment. Further, it is desirable to have a seal which will operate over a broader range and reduce any ultimate seal wear by obtaining an optimum film thickness over a wide range of operating conditions.